如何从仅出现在console.log（）中而不出现在JSON.stringify（）中的JavaScript对象中获取属性？

Question

I'm getting an error object back from my SQLite database. When I display it with console.log(err) , I get:

{ records: { Error: SQLITE_ERROR: no such table: showcaseUsers errno: 1, code: 'SQLITE_ERROR' } }

Yet when I display it with JSON.stringify(err) , I only get:

{"records":{"errno":1,"code":"SQLITE_ERROR"}}

I want to get the error message no such table: showcaseUsers in a string.

The only way I have found how to do this is with this:

const errorText = console.log(data);

But this also outputs the data to the console, which is undesirable.

How can I either (1) stop console.log from outputting its content to the console, or else (2) get the error message in a string some other way?

NOTE: I am in Node at this point and not in a browser, so it doesn't seem that the answer at Capturing javascript console.log? is helpful.

Answer 1

There's no need to intercept the console at all - you will find the entire error message in err.message , albeit still prefixed with " SQLITE_ERROR: "

It's a non-enumerable property of the Error object hence why it doesn't appear in the JSON output:

let sqlite3 = require('sqlite3');

let db = new sqlite3.Database(':memory:');
db.run("UPDATE foo SET bar = 1", (err, res) => {
  console.log(Object.getOwnPropertyDescriptors(err));
  console.log(err.message);
});

with output:

{ stack:
   { value: 'Error: SQLITE_ERROR: no such table: foo',
     writable: true,
     enumerable: false,
     configurable: true },
  message:
   { value: 'SQLITE_ERROR: no such table: foo',
     writable: true,
     enumerable: false,        <<---------
     configurable: true },
  errno:
   { value: 1, writable: true, enumerable: true, configurable: true },
  code:
   { value: 'SQLITE_ERROR',
     writable: true,
     enumerable: true,
     configurable: true } }
SQLITE_ERROR: no such table: foo

Answer 2

Issue is wrongly formatted JSON, which must be key:value pairs. If value in key:value is a string then it should be enclosed in single or double quotes.

{ records: { Error: SQLITE_ERROR: no such table: showcaseUsers errno: 1, code: 'SQLITE_ERROR' } }

In the absence of proper value ( value in your case has datatype String ), JSON.stringify(err) tries to coerce it to JSON based on colon : as separator between key and value . Available datatypes in JavaScript

Here is a correction, I have just enclosed it in double quotes, and formatted it (formatting is optional, helpful for legibility).

{ 
    records: { 
        Error: "SQLITE_ERROR: no such table: showcaseUsers errno: 1, code: 'SQLITE_ERROR'" 
    } 
}

Actually it should be formatted (see placement of single quotes) like so

{ 
    records: { 
        Error: 'SQLITE_ERROR: no such table: showcaseUsers',
        errno: 1, 
        code: 'SQLITE_ERROR'
    } 
}

Update: It's imperative to store properly formatted data in database in the first place. If you missed it then you are left with manually parsing data you are getting from SQLite.

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• How to store JSON object in SQLite database
• Use the new JSON extension for SQLite with Python
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